1. Technical Field
The present invention relates to a virtual image display apparatus and a projector that present a video formed by a video display apparatus to an observer and, more particularly, to a virtual image display apparatus suitable for a head mounted display mounted on the head of the observer.
2. Related Art
Various virtual image display apparatuses are proposed as a virtual image display apparatus such as a head mounted display (hereinafter also referred to as HMD) mounted on the head of an observer (see, for example, JP-A-2012-163640 (Patent Literature 1)).
The virtual image display apparatus such as the HMD is desired to attain an increase in an angle of view without deteriorating image quality while being reduced in size and weight. If the virtual image display apparatus covers the entire visual field of the observer to allow the observer to see only video light, the observer cannot see a state of the outside world and feels uneasiness. A new use such as virtual reality is created by superimposing and displaying the outside world and a video and allowing the observer to see the video through the outside world. Therefore, there is a demand for a display that displays video image light to be superimposed on the outside world without hindering a visual field of the outside world.
Taking into account the situation explained above, a transparent light guide device arranged in front of the eyes of the observer by see-through is used. Consequently, it is possible to form a virtual image display apparatus in a form close to eyeglasses, improve a wearing feeling, and improve an apparent form. In this case, it is conceivable that an optical system for causing the observer to visually recognize an image has, for example, a form for guiding video light formed by a liquid crystal display panel arranged on a head side surface and a projection optical device to the front of the eyes using a transparent prism (see Patent Literature 1).
However, the virtual image display apparatus is mounted with an optical unit such as a liquid crystal display panel. Therefore, for example, as disclosed in Patent Literature 1, when a video display device and a projection optical system are arranged on the side head of the observer, since large devices are present around the side head, compared with the normal eyeglasses, protrusions are extremely conspicuous when the virtual image display apparatus is worn. The appearance of the virtual image display apparatus tends to be deteriorated.
On the other hand, from the viewpoint of protection of an optical system, for example, it is also conceivable to form an external appearance using a case-like member for protecting the entire optical system. However, in this case, the shape of the virtual image display apparatus tends to increase and the weight also tends to increase. When long-time use and convenience for carry-out and the like are taken into account, as the HMD, it is desirable that the virtual image display apparatus is small in size and weight as much as possible.